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BQ40Z50-R1: PRES pin cannot pull high

xiji xiao
Prodigy 20 points
Part Number: BQ40Z50-R1
Other Parts Discussed in Thread: BQ40Z50

I want use PRES pin to control CHGFET and DSGFET .I set NR bit to NR=0,PRES pin through a 100 ohm resistor in series connected to a 3.3 V MCU IO.

when I set MCU IO as push-pull mode and set IO output high level voltage ,operation status->PRES bit can be  clear ,CHGFET and DSGFET can be turn off. but the PRES pin voltage only 0.3V ,100 ohm resistor have 10mA current.

when I release PRES pin ,config MCU IO as OD mode ,Power consumption is normal, but cannot turn off CHGFET and DSGFET.

only set NR=0 then reset device or device in ROOM mode ,I can set MCU IO as push-pull mode and set IO output high level voltage with normal consumption.

Where configuration error will cause the BQ40Z50 pull down the PRES pin?

  • 0
    Prodigy 50 points

    Hi,

    I have the same issue, although my HW setup is a bit different. In my setup I have an external 10k PU to 3V3, which is supposed to keep the signal high even though FG is pulsing the PRES pin to save power. In my application the PRES signal is also connected to an MCU to give an interrupt when the pack is inserted to a system.

    It seems that FG is driving the PRES pin low during the low period of the pulsing. Is there any way to disable this feature? If NR bit is set to 1 the PRES pin can be pulled high. But then I loose the PRES detection functionality on FG.

    BR,

    Antti

  • 0 in reply to Antti Paajanen
    TI__Expert 6575 points

    The PRES pin is not a true input. PRES is only detected when the pin is pulled low, and will be de-asserted when it's floating. It can not be pulled high.

    Please see the guideline below: